In recent years, with the global movement of saving energy including electricity, there is a strong demand for higher efficiency in electric appliances, and an even lower iron loss is desired for non-oriented electrical steel sheets used in iron core materials as well. Therefore, various proposals have been made for iron loss reducing techniques for non-oriented electrical steel sheets.
As a measure to reduce iron loss of non-oriented electrical steel sheets, a means of increasing the content of Si, Al, Mn, or the like in steel to increase electric resistance and reduce eddy current loss, is generally used. However, if the addition amounts of Si, Al or the like are increased for the purpose of further improving iron loss properties of the current high-grade products, not only problems relating to manufacturability such as rolling, but also a disadvantage of causing an increase in material costs is caused.
JPH0250190B (PTL 1) discloses a technique of reducing iron loss by reducing the content of impurity elements (S, N, and O) in steel. Further, JP2984185B (PTL 2) discloses a method of suppressing mixture of impurities and defining the slab heating temperature, the coiling temperature, the hot band annealing condition, the cold rolling reduction ratio, and the final annealing condition to control inclusions and reduce iron loss.
Further, some methods of modifying the production process to improve the crystal orientation distribution in the product sheets, i.e. the texture thereof to enhance magnetic properties, have been proposed. For example, JPS58181822A (PTL 3) discloses a method of subjecting a steel containing Si: 2.8 mass % to 4.0 mass % and Al: 0.3 mass % to 2.0 mass % to warm rolling in a temperature range of 200° C. to 500° C. to develop {100}<0VW> textures. Further, JPH03294422A (PTL 4) discloses a method of subjecting a steel containing Si: 1.5 mass % to 4.0 mass % and Al: 0.1 mass % to 2.0 mass % to hot rolling, and then performing hot band annealing at 1000° C. or higher and 1200° C. or lower in combination with cold rolling at a rolling reduction ratio of 80% to 90% to develop {100} textures.
Further, JPS5654370B (PTL 5), JPS583027B (PTL 6), and JP4258164B (PTL 7) propose a technique of containing a small amount of Sn or Sb to reduce iron loss.